It is well known in the art to provide tillage machines with double axle walking beam undercarriages. Such a walking beam undercarriage spreads the load over a pair of axles at each wheel assembly and helps smooth out the ride as the undercarriage traverses uneven terrain. However, as tillage implements become bigger and heavier, there is a need for additional load support spread over additional axles, particularly for the center section of a folding winged implement in which the weight of wing sections is borne by the center section when the wing sections are folded for transport.
Accordingly, the present invention provides a triple axle walking beam undercarriage that provides increased load support and smoother ride than available with conventional double axle walking beam assemblies. Whereas in a conventional double axle assembly a single walking beam having one wheel axle at the front and another at the rear oscillates freely about a central, transverse axis as the wheels successively “walk” over obstacles, in the present invention the single beam is replaced by a pair of hingedly interconnected beams comprising a primary beam and a secondary beam. The primary beam is pivotally attached to the wheel lift arm of the chassis for oscillation about a primary transverse axis, while the secondary beam is pivotally attached to the rear of the primary beam for oscillation relative to the primary beam about a secondary transverse axis. The secondary beam has a pair of ground wheels attached to front and rear ends thereof for supporting the rear end of the primary beam, while the primary beam itself has a single wheel attached to the front end thereof. In this manner, additional load support is provided by the three axles associated with the three ground wheels, yet each of the wheels can oscillate up and down independently of the others as need be to smooth out the ride.
The present invention also provides a way of transferring some of the weight of the machine from the front wheel of the walking beam assembly to the rear wheels when the chassis of the machine is raised to a fully lifted position such as occurring at the end of the field when the machine is lifted and turned for the next pass. Although such weight transfer arrangement is beneficial in a triple axle system, the principles are also of value in a double axle system.
Such weight transfer is accomplished through the provision of an abutment on the wheel lift arm that comes into abutting engagement with a stop on the walking beam assembly after the wheel arm has swung down to a predetermined extent relative to the rising chassis. Whereas prior to such abutting engagement the load is fairly equally distributed over all wheels of the walking beam assembly, once the abutment engages the stop, the walking beam assembly is essentially locked up against oscillation in one direction such that further downward swinging of the wheel arm tends to lift the front wheel and exert additional loading on the rear wheel or wheels. This keeps the point of major ground support located far enough rearwardly with respect to the center of gravity of the chassis that tongue weight is increased and the chassis is prevented from becoming “tail heavy.” Without the weight transfer arrangement, the machine could suddenly become tail heavy when it is raised during turns at the end of the field, causing the hitch connection at the front end of the tongue to slam up against the tractor draw bar, damaging the equipment and jarring the operator. Preferably, the stop that is engaged by the abutment on the wheel arm is made of resilient material to provide a cushioning effect during engagement of the abutment with the stop.